Electric field-induced crystallization of ferroelectric hafnium zirconium oxide

Maximilian Lederer,Thomas Kämpfe,Sukhrob Abdulazhanov,Ricardo Olivo,David Lehninger,Lukas M Eng,Konrad Seidel

doi:10.1038/s41598-021-01724-2

Abstract

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications. Especially for back-end-of-line (BEoL) integration the decrease of crystallization temperature is of major importance. However, an alternative method for inducing ferroelectricity in amorphous or semi-crystalline hafnium zirconium oxide films is presented here, using the newly discovered effect of electric field-induced crystallization in hafnium oxide films. When applying this method, an outstanding remanent polarization value of 2P_{mathrm{R}} = 47 upmuC/cm^{2} is achieved for a 5 nm thin film. Besides the influence of Zr content on the film crystallinity, the reliability of films crystallized with this effect is explored, highlighting the controlled crystallization, excellent endurance and long-term retention.

Highlights

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications
As many HfO2-based devices can be integrated into the back-end-of-line (BEoL), recent publications focused on hafnium zirconium oxide (HZO), which enables crystallization at low temperatures, compatible with the BEoL thermal budget requirements[8,9]
Recent works discovered a new effect in the hafnium oxide system, namely electric field-induced crystallization[10]

Summary

Introduction

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications. This allows to apply electric fields in order to crystallize the hafnium oxide film directly into the ferroelectric phase, as illustrated, with an effective activation energy of 0.45 eV10. Rather a crystalline phase with a non-centrosymmetric space group, is required for the presence of ferroelectricity, this clearly indicates electric field-induced crystallization for the Hf-rich films.

Results

Conclusion